1. Field of the Invention
This invention relates to a process for producing a dried banana product, and more specifically, to a process for producing a dried banana product having a crisp texture and good storage stability by frying slices of fully ripe raw banana flesh in an edible oil under reduced pressure thereby to dehydrate the banana flesh.
2. Description of the Prior Art
Fully ripe raw banana flesh generally comprises, by weight, 75.5% water, 1.3% protein, 0.4% lipid, and 21.4% carbohydrate. About 90% of the carbohydrate comprises sucrose and reducing sugars, and starch accounts for about 2% of the entire banana. In addition to these components, ripe raw banana flesh contains some amount of crude fiber, ash and organic acids and small amounts of inorganic substances, vitamins, pigments, tannins, and enzymes.
Drying of ripe raw banana flesh having such a composition is limited in many ways. For example, since the flesh contains a large amount of sucrose and reducing sugars, the flesh has a low water activity. This makes dehydration of the flesh difficult, and long periods of time are required for drying the flesh. Consequently, browning of the banana flesh occurs due to the presence of a group of enzymes such as polyphenoloxidases, and peroxidases, and the quality of the ripe raw banana is reduced.
In conventional methods for producing dried banana products, therefore, the usual practice is to inhibit the activities of these enzymes by immersing the banana flesh in a solution of SO.sub.2 or another sulfur dioxide generating agent or a solution of a browning inhibitor such as ascorbic acid. A blanching treatment with hot water or steam is another conventional means of inhibiting browning.
Ripe fruit inherently has a larger moisture content than unripe fruit, and contains less starch and crude fiber and more sugars. Thus, the texture of ripe fruit is soft and weak. When the ripe banana flesh is subjected to a blanching treatment, the water content of the flesh is increased, and therefore, the texture of the ripe banana flesh is further softened. Hence, subsequent handling of the banana flesh in drying causes crumbling or deformation of the ripe banana flesh to occur.
It is extremely difficult to dry slices of ripe raw banana flesh while retaining their shape. For this reason, according to conventional techniques, a dried banana product generally called banana chips is produced by using flesh of unripe bananas having a solid texture and a total sugar content of as small as less than about 2% by weight as a starting material, and drying the flesh after subjecting the flesh to a blanching treatment with hot water or steam, and/or after immersing the flesh in a solution of SO.sub.2 or another sulfur dioxide generating agent or a solution of a browning inhibitor such as aluminum chloride, citric acid or ascorbic acid.
Naturally, the resulting dried banana products obtained lack the sweet taste, the unique flavor, the unique color, etc. which are inherent to ripe raw bananas. The banana products are therefore processed further by, for example, treating the products with a solution of sugar and/or a gelatinous substance, or adding artificial flavors, dyes, etc. to enhance their flavor and color before they are marketed as final products.
On the other hand, products generally called banana powder or banana flakes are made from ripe bananas as a starting material. In order to facilitate drying, the bananas are mashed into a paste form, and then dried using a method such as foam mat drying, drum drying or low-temperature vacuum drying. These products do not have the original shape of a banana, and differ markedly from the dried banana products which are obtained by the process of the present invention.